The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Because frequency spectrum is a limited resource, several communication systems may share the same spectrum. In a given frequency spectrum a given number of frequency bands may be given to different operators or carriers in different locations. Typically each operator performs independent cellular coverage planning.
Present day methods for measuring cellular coverage in a cellular carrier's networks utilize radio scanners which operate in the cellular frequency bands. Typically, a route is driven using a vehicle equipped with the scanner equipment for collecting over-the-air downlink signals from the carrier's cell sites. Satellite positioning systems such as Global Positioning System GPS or Global Navigation Satellite System GLONASS is used to geographically map the coverage area using specific signaling parameters for a given cellular technology. For Global System for Mobile communication (GSM) systems, signaling parameters measured and collected include received signal strength (RSSI), carrier-to-noise plus interference (CINR), the base station identifier code (BSIC), and broadcast channel (BCCH) messages.
The scanners require stable frequency reference to be able to tune to unknown signals. Present-day equipment typically rely on GPS signals to obtain a frequency reference. However, there may be situations where GPS signals are not available. Thus, there is a need for an alternate frequency reference. The same applies to timing references. GPS may be used to obtain a stable timing reference. In the absence of a GPS signal, an alternate way of obtaining a timing reference is required.